docs: def assert_datetime_about_now(actual, msg_fmt="{msg}"):
      """Fail if a datetime object is not within 5 seconds of the local time.
  
      >>> assert_datetime_about_now(datetime.now())
      >>> assert_datetime_about_now(datetime(1900, 1, 1, 12, 0, 0))
      Traceback (most recent call last):
          ...
      AssertionError: datetime.datetime(1900, 1, 1, 12, 0) is not close to current date/time
  
      The following msg_fmt arguments are supported:
      * msg - the default error message
      * actual - datetime object to check
      * now - current datetime that was tested against
      """
  
      now = datetime.now()
      if actual is None:
          msg = "None is not a valid date/time"
          fail(msg_fmt.format(msg=msg, actual=actual, now=now))
      lower_bound = now - timedelta(seconds=_EPSILON_SECONDS)
      upper_bound = now + timedelta(seconds=_EPSILON_SECONDS)
      if not lower_bound <= actual <= upper_bound:
          msg = "{!r} is not close to current date/time".format(actual)
          fail(msg_fmt.format(msg=msg, actual=actual, now=now))